BIB Design Criteria

[topgun 262]

Ok, here is what I have gathered on the design of BIB enclosures, I have compiled this from www.diyaudio.com.

BIB Design Criteria

o It is a

[topgun 262]

Also thoughts on mounting a second driver on the inside baffle for a boost. *from Scottmoose on DIY Audio*

Yes, adding a second driver mounted through the internal baffle is an interesting idea for a bit of tapped-horn boost. Note that Vb will have to double though -something of a downside when a cabinet is already rather large. ;^) Wish I'd thought of it, but GM takes credit for that one. No, it wouldn't necessarily have to be at the same height as the forward-firing unit, though it it would be advantageous IMO. Overall, I suspect it would end up being somewhat design-specific as to where it will best be positioned. I can't see there being a major problem of cancellation occurring, assuming the correct placement of the drivers so that the wavefronts do not encounter something in the reverse-phase.

[ANeonRider 3]

Nice to see the design summed up like this!

Using the dimensions I used for my BIB build:

Line length = 136"

1/2λ Fb = 50Hz

0.707*Fs(68Hz) = 48Hz

I was safe there

Vb = 29.16L

Vas = 5.8L

Qts = 0.64

20Vas*(Qts^1.25) = 20(5.8)*(0.64^1.25) = 116*0.572 = 66.352L

D/W ratio = 1.315:1

Good as well.

Driver location on baffle (So) = 36.5" from top

With line length of 68", that works out to 0.5367.

Good to see what I put together follows the criteria you summed up

[topgun 262]

The numbers have been verified, and I have updated the Vb calculation so everything is correct.

[DevilDriver 28]

o It is a

[topgun 262]

o It is a

[///M5 2,833]

Nice work mang!

[topgun 262]

Thanks Sean.

Also, if anyone wants to simulate these, the Martin King worksheets will do these, you have to look on diyaudio.com for the particulars though since I haven't done it yet.

Link to the worksheets

http://www.quarter-wave.com/Models/MathCad_Models.html

[DevilDriver 28]

Yes. This is a TQWT (Tuned Quarter-Wavelength Tube) design that Terry Cain developed after reading the Fostex Craft Handbooks which were widely available in Japan and very hard to find here. If I remember the backstory correctly, apparently the Japanese have a fairly engrained knowledge of speakers...even being able to learn acoustics in lower-level education facilities.

edit: As always, James Melhuish's site comes through.

And yes, if simulation is your game, you simply must get MJK's MathCAD sheets. Martin is also kind enough to explain the derivation of the formulas used and how to do the simulations. Don't be afraid to jump in.

[ANeonRider 3]

The Vb I used is ~1/2 the Vb that is calculated. Not entirely sure how critical it is?

[ANeonRider 3]

http://www.diyaudio.com/forums/showthread....threadid=112653

[Aaron Clinton 2,372]

Very nice, I hope to have a chance to build one next season.

[Ga foo 88 0]

I was searching another diy forum and they seem to conclude thatt the BIB horns were quite forgiving of building somewhat off the guidelines set for each driver. Looking at the extended bass horns with the normal 6.5 drivers on their webpage, could you run a 6.5/7 in 2 way system with a BIB. Say for instance i have some AA poly mids laying around, would they work or would it be an experimentation type ordeal?

Also is there any way you could have 2 or 4, 3in mid ranges (just an example) in a BIB? There are t-line designs that are 2-way, and the tri-trix is visually similar, but what do yall think?

Edited December 11, 2007 by Ga foo 88

[JimJ 11]

Looking at the extended bass horns with the normal 6.5 drivers on their webpage, could you run a 6.5/7 in 2 way system with a BIB.

I think that'd be something worth exploring...

[Ga foo 88 0]

I thought it would be cool to have the AA mid or Mach5 mid in a BIB and Ixl15 in a sontube, and keep it all ssa, plus the tweeter ofcourse... if its possible.

[JimJ 11]

One issue with adding crossovers and drivers and such is that you lose the sense of coherency and true point source that you get with a single driver...not saying it's bad, it's just different

[Ga foo 88 0]

I was wondering some of the effects, thanks for the input. I think i might try the 4" bamboo tb full rangers since they are cheap.